Firebug 1.1 is Firebug 1.05 by Joe Hewitt with enhancements and bug fixes by John J. Barton (IBM Almaden) and Max Stepanov (aptana)
The file is an XPI file that will add-on to Firefox as Firebug v1.1. Firefox’s updater will allow you to get new experimental versions until Firebug 1.1 is official.
